1. Field of the Disclosure
The disclosure relates generally to media processing devices, and, more particularly, to a nip mechanism for processing a media sheet in a media processing device.
2. Description of the Related Art
Media processing devices are widely used in offices, in homes and in business enterprises for processing media sheets. The processing of a media sheet may include outputting information onto the media sheet. The information transferred onto the media sheet may be adhered onto the media sheet by application of heat and pressure for outputting the information onto the media sheet. A media processing device may be configured to advance the media sheet through a nip configured by a heater device and a pressure roller, for applying the heat and the pressure respectively, for adhering the information onto the media sheet and for outputting the information from the media processing device.
In a media processing device, such as a printer, the media processing device outputs information displayed on a screen of a data processing device onto a media sheet, such as a sheet of paper. Such a media processing device may include an electrophotographic imaging assembly for outputting information onto the media sheet. The electrophotographic imaging assembly typically includes a photoconductive member, a light source, a toner, a media feed assembly and a nip mechanism. The photoconductive member is typically homogenously charged. Based on the information to be output on the media sheet, the light source focuses a light beam onto the photoconductive member to create a charge pattern on the photoconductive member. Toner particles of the toner are electrostatically attracted to the charge pattern to form a latent image which may then be transferred to the media sheet to form an image on the media sheet.
The image formed on the media sheet includes unfused toner particles. The unfused toner particles need to be fused by forcing the unfused toner particles to adhere to the media sheet. The media sheet may be advanced using the media feed assembly to the nip mechanism for fusing the toner particles onto the media sheet. The nip mechanism may typically include a pressure roller and a heater device capable of abuttingly coupling to the pressure roller to form a fuser nip for applying heat and pressure onto the unfused toner particles for permanently fixing the image onto the media sheet. The media sheet is advanced through the fuser nip for fusing the toner particles onto the media sheet. The high temperature melts the toner particles and the pressure forces the toner particles to adhere to the media sheet.
The heater device may include a belt configured to enclose a heating element. A first surface of the belt may be configured to contact the pressure roller to form the nip, such as the fuser nip. The belt is typically coated with a compliant material to increase size of a processing region and to aid in release of the media sheet and the toner particles. The complaint material may become permanently deformed, i.e., compressed, on being subjected to the pressure for prolonged period of time. The deformation of the compliant material may lead to processing defects and torque spikes during processing of the media sheet. To prevent the deformation of the compliant layer, a nip release mechanism is typically included in the media processing device. The nip release mechanism may be configured to engage the nip, i.e., abuttingly couple the heater device to the pressure roller, on generating a signal, such as a signal for processing the media sheet. The nip release mechanism may further be capable of uncoupling the heater device from the pressure roller on completion of the processing of the media sheet. The nip release mechanism is typically configured with a closed-loop control actuated through a feedback loop with a sensor operatively coupled to the nip release mechanism and motion of a motor, such as a fuser motor for controlling the pressure in the nip. Such nip release mechanisms require software sensing and hardware to decrease the pressure in the nip, and as such may be expensive.
Cheaper alternatives, such as an automatic nip release mechanism with no feedback may also be configured for providing ability to reduce the pressure between the heater device and the pressure roller without the use of a sensor feedback loop. The automatic nip release mechanism may utilize a mechanical motion sensing mechanism, such as a swing arm, in conjunction with a sector gear for reducing the pressure in the nip. The automatic nip release mechanism, however, does not include a feedback loop, and as such may fail to detect a failure of the nip to close on generating the signal for engaging the nip. The nip may fail to close due to reasons such as failure of the swing arm to rotate for engaging the nip, poor quality of hardware components used for engaging the nip, wearing of the hardware components, and the like. The failure to detect the closure of the nip prior to performing the processing of the media sheet may be critical for avoiding processing quality problems, poor fuse grade problems, cold offset and the like.
Based on the foregoing, there is a need for processing a media sheet by advancing the media sheet through a nip configured to apply heat and pressure onto the media sheet. Further, there exists a need for verifying a closure of the nip prior to advancing the media sheet through the nip for processing the media sheet. Furthermore, there exists a need for verifying the closure of the nip precluding use additional sensors for reducing cost and mechanical complexity.